The present invention really relates to a block construction of an engine and, more particularly, to a passage construction of the cooling water in an engine having the block integrally cast, the block being provided with a head portion and a cylinder portion.
Generally, in the engine for motor cars, a head portion having an air inlet/exhaust ports is formed on the cylinder head, and a cylinder portion having a cylinder bore and a skirt portion for constructing a crank chamber are formed integrally on the cylinder block. However, according to such engine construction as described hereinabove, a plurality of head bolts are required to be disposed astride the cylinder block from the upper portion of the cylinder head, avoiding interferences with air inlet/exhaust ports, air inlet/exhaust valves or the like. Thus, the layout of the air inlet/exhaust system is subjected to the restriction of the bolt to considerably lower the degree of the freedom, and the both face between the cylinder head and the cylinder head is deformed under the influences of the combustion gas of high temperature and high pressure, so that the sealing property of the butt face with respect to the combustion gas becomes considerably deteriorated in the engine of high output and high rotation.
In order to cope with such a problem, a position astride the cylinder portion from the head portion is integrally formed with one block to remove the head bolt as shown in, for example, Japanese Patent Application Laid-Open Publication (Tokkaisho) No. 56-34938 and Japanese Patent Application Laid-Open Publication (Tokkaisho) No. 54-137512. The butt face between the block and the other block is adapted to be not located in the position corresponding to the combustion. Accordingly, the block construction of the engine is proposed wherein the sealing property with respect to the combustion gas is adapted to be improved with the freedom degree of the layout of the air inlet/exhaust system being enlarged.
However, as the construction of the cooling water passage (water jacket) provided on the head portion and the cylinder portion is not proper even if the engine block construction is of either one of both the above-mentioned publications, the cooling operation of the engine is not properly performed.
According to the Laid-Open publication of Japanese Patent Application (Tokkaisho) No. 56-34938, the cooling water passage is integrally formed astride the head portion and the cylinder portion, and a partition wall (lower deck) or the like is not provided between them, so that the flow speed of the cooling water passing through the passage is extremely delayed, and the cooling water of the high temperature may remain above the combustion chamber requiring the cooling effect most. In the multiple cylinder engine, the flow of the cooling water passing through the cooling water passage becomes uneven to cause dispersion in the cooling operation for each cylinder. The flow of the cooling water becomes stagnant particularly between the adjacent cylinders because of the passage shape or the layout, so that the cooling property with respect to the position is considerably deteriorated.
Also, in the Laid-Open publication of Japanese Patent Application (Tokkaisho) No. 54-137512, the inner wall (peripheral wall) of the cylinder is vertically extended to connect the inner water with the outer wall by the partition wall a little above the combustion chamber, and the passage to be formed between the inner wall and the outer wall is provided as the cooling water passage on the side of the cylinder with a through hole being formed at the direction of a nozzle or the like in its upper portion. Although the cooling property is considered to be partially improved with the through hole being directed at the nozzle, it is needless to say that the unification of the cooling operation for each cylinder and the cooling operation with respect to the portion between the adjacent cylinders are spoiled. The cooling operation with respect to the top wall of the combustion chamber is effected by the cooling water of the high temperature which flows into the cooling water passage on the side of the head portion after the heat exchange on the cooling water passage on the side of the cylinder portion, so that it is difficult to efficiently and positively lower the temperature of the combustion chamber. Also the cooling operation with respect to the combustion chamber is not properly performed, so that various harmful effects such as knocking, overheat and so on are caused in the high load of the engine producing more calorific values.